1. Field of the Invention
This invention relates generally to pumps and more particularly to piston type fluid intensifiers.
2. Description of the Prior Art
Fluid intensifiers utilize the energy of a low pressure fluid to pump out a portion of the fluid at a higher pressure. Fluid intensifiers are sometimes used as water pumps in remote areas where conventional power sources are not available.
There are two common types of fluid intensifiers, namely "ram" type intensifiers and piston type intensifiers. U.S. Pat. No. 4,212,597 of Mallofre describes a piston type intensifier including a main cylinder provided with a high pressure outlet, a control cylinder provided with a low pressure inlet, a spool disposed within the control cylinder, and a multi-head piston disposed within the main cylinder. When a pressurized fluid source is applied to the low pressure inlet, the multi-head piston is caused (under the control of the spool) to reciprocate within the main cylinder assembly to develop a high fluid pressure at the high pressure outlet.
A problem with prior art piston type fluid intensifiers is that they require a very stable, continuous fluid source in order to operate. Piston type fluid intensifiers tend to become stuck in mid-cycle if the fluid source is interrupted because they depend upon the momentum of continuous operation to control the stroke direction of the pump pistons. If the pump pistons are stopped in mid-cycle by a loss of fluid source pressure, they could equally well move in either direction when fluid source pressure is reapplied. Rather than move in one direction or the other, the pump pistons often jam.
Some prior art piston type fluid intensifiers address this problem by providing biasing mechanisms to prevent the intensifier mechanism from becoming stuck in mid-cycle. For example, Wrigley in U.S. Pat. No. 2,826,149 provides a spring-loaded over-center mechanism for just such a purpose. Problems with biasing mechanisms is that they too can become stuck, and that they add to the cost an intensifier.
Another drawback of prior art piston type intensifiers is that they are often difficult to disassemble for repair or inspection. Due to this limitation, it is difficult to vary the pumping ratio for most prior art piston type intensifiers.
A problem with ram type fluid intensifiers is that they often require priming. For example, most ram type water pumps require manual priming at the start of operation and repriming when they run dry.
Because of these problems, fluid intensifiers have not been utilized extensively. What the prior art fails to disclose, then, is a fluid intensifier which does not require priming, which can operate from an erratic fluid source, and which can be easily disassembled for repair and modification.